In most Gram-negative pathogens, genes involved in iron acquisition and virulence are transcriptionally regulated by the availability of iron through the ferric uptake regulator protein, Fur. The etiological agent of the sexually transmitted disease gonorrhea, Neisseria gonorrhoeae, produces a number of iron regulated proteins which are utilized for iron transport and expression of these proteins is thought to be under the control of Fur; however, the role of Fur in controlling expression of iron transport genes or virulence factors in N. gonorrhoeae is not well defined. This application proposes to further our understanding of the regulation of genes involved in iron transport and virulence by the transcriptional regulator protein Fur, and to define the role of the Fur-regulon in N. gonorrhoeae pathogenesis. Our hypothesis is that Fur controls the expression of a number of genes in addition to iron transport genes that are required for the virulence of N. gonorrhoeae. The specific aims of this proposal are as follows: Aim 1.To identify the minimal essential gonococcal nucleotide sequence for Fur binding and characterize the interactions of gonococcal Fur with iron-regulated promoters. Aim 2.To isolate and characterize iron-independent mutants of gonococcal Fur. Aim 3. To define the Fur regulon in N gonorrhoeae. Aim 4.To define the role of the gonococcal Fur regulon in pathogenesis. These studies are based on the premise that gonococcal Fur binds to a unique and specific array of DNA sequences within the promoter regions of a number of Fur-regulated genes. This allows gonococcal Fur to function as a general global regulator controlling the expression of numerous genes in Neisseria. The intracellular iron concentration and the variability and extension of sequences targeted by Fur may cause a wide range of responses. Therefore, there may be many genes that are regulated by Fur that are unidentified. The results obtained in these studies will enable us to define the binding of gonococcal Fur to gonococcal Fur-regulated promoters, to identify additional genes which are regulated by Fur in N. gonorrhoeae, to define the mechanisms of Fur mediated regulation, and to correlate this with the pathogenic potential of N gonorrhoeae.